1. Field of the Invention
The present invention relates to a detection device which detects a state of a tubular body. Examples of such state are: presence or absence of a tubular body at a specified position type of diameter (inside diameter, outside diameter, and wall thickness) of the tubular body; presence or absence of a fluid such as liquid flowing through the tubular body; the type of the fluid, in particular liquids; presence or absence of an air bubble in a liquid; and state related to the tubular body at the specified position and to a fluid, in particular liquid, flowing through the tubular body.
2. Description of the Related Art
Conventionally, the devices disclosed in JP-A-2012-205866 and JP-A-2007-296134 have been developed as a detection device of this kind, particularly, a detection device for detecting an air bubble in liquid such as a medical solution or dialysis solution flowing through a transfusion tube (tubular body).
The detection device disclosed in JP-A-2012-205866 is a device in which an ultrasonic sensor is used as means for detecting an air bubble in a transfusion tube, and the presence/absence of such an air bubble is determined based on the propagation efficiency of ultrasonic waves in the transfusion.
In the detection device disclosed in JP-A-2007-296134, a capacitance is configured in which members that cause opposed portions of the outer circumferential surface of a transfusion tube to be flattened, and that nip the tube are used as one set of electrodes, and thick portions of the transfusion tube, and the volume part of the transfusion tube sandwiched between the one set of electrodes are used as a capacitor capacitance. The device detects an air bubble entering the transfusion tube based on the capacitor capacitance which varies in accordance with the presence/absence state of liquid in the volume part.
However, in the detection device which is disclosed in JP-A-2012-205866, and in which an ultrasonic sensor is used, ultrasonic transmission and reception parts must be placed so as to be opposed to each other. Therefore, the sensor is difficult to be produced, and its production cost is high. The device has a complicated structure, and hence it is difficult to clean the device. In order to ensure the accuracy, moreover, the transfusion tube must be in close contact with a sensor portion. Consequently, there is a possibility that the durability of the transfusion tube is lowered.
In the detection device which is disclosed in JP-A-2007-296134, and which operates based on the capacitor capacitance, the transfusion tube must be deformed, and hence there is a possibility that the transfusion tube is damaged or its lifetime is shortened. Moreover, the electrodes must be opposedly placed. Therefore, the device has a complicated structure, and hence it is difficult to clean the device.